1. Field of the Invention
The present invention relates to a method for forming wiring of a semiconductor device.
2. Description of the Related Art
For multilayer wiring to be formed, for example, in a semiconductor device such as a transistor, Cu wiring is applied to realize a high speed semiconductor device. As a method for forming the Cu wiring, a dual damascene method is used in which connection holes (for example, contact holes, via holes) and wiring grooves are formed in a multilayer film structure and then the connection holes and wiring grooves are filled with Cu material at a time. The dual damascene method has an advantage in that it has a smaller number of steps, so that the manufacturing cost can be reduced.
The method for forming Cu wiring using the conventional dual damascene method will be described here using FIGS. 13A to 13I. First of all, for example, a wiring layer 200, an interlayer insulation film 210, and an antireflection film 202 are formed on a substrate in order from the bottom, and a first resist film 203 is formed on the surface of a multilayer film structure composed of those layers (FIG. 13A). Then, the first resist film 203 is patterned into a predetermined pattern by the photolithography technique (FIG. 13B).
In this patterning step, the first resist film 203 is exposed to light under the predetermined pattern, and a resulting exposed portion is selectively removed by development. Subsequently, the antireflection film 202 and the interlayer insulation film 201 are etched by etching treatment using the first resist film 203 as a mask. Thus, a connection hole 204 is formed which leads to the wiring layer 200 from the surface of the multilayer film structure (FIG. 13C).
Then, the first resist film 203 which is unnecessary any longer is removed by stripping, for example, by ashing treatment (FIG. 13D), and a second resist film 205 for forming a wiring groove is newly formed instead (FIG. 13E).
The second resist film 205 is patterned by the photolithography technique (FIG. 13F), and then the antireflection film 202 and the interlayer insulation film 201 are partially etched by the etching treatment using the second resist film 205 using as a mask.
Thus, a wiring groove 206 is formed which communicates with the connection hole 204 and is larger in width than the connection hole 204 (FIG. 13G). The second resist film 205 which is unnecessary any longer is removed by stripping (FIG. 13H), and the connection hole 204 and the wiring groove 206 are filled with Cu material, thus forming a Cu wiring 207 (FIG. 13I) (Japanese Patent Laid-open No. 2002-83869).
Conventionally, the above-described ashing treatment when removing the first resist film 203 has been performed by supplying a nitrogen gas and a hydrogen gas or an ammonia gas into a treatment container to expose the substrate to the atmosphere. Therefore, during the ashing treatment, a very small amount of ammonia component has been sometimes absorbed in the interlayer insulation film 201 exposed due to the connection hole 204. Also in the interlayer insulation film 201 such as a low dielectric constant film itself, which often contains nitrogen atoms in its compositional components, a very small amount of basic amine has been generated, for example, during film formation and remained.
As described above, the interlayer insulation film 201 has often contained the amine component at the time when the first resist film 203 is removed by stripping. Incidentally, there is another conceivable factor of absorption of the amine component into the interlayer insulation film 203, such as use of an ammonium fluoride-based or amine-based treatment solution, for example, when the first resist film 203 is removed with the treatment solution, or generation of the amine component, for example, when the etching for formation of the connection hole or cleaning of the connection hole is performed.
Accordingly, when the second resist film 205 is formed after the removal by stripping of the first resist film 203, the amine component in the interlayer insulation film 201 permeates the adjacent second resist film 205, whereby the second resist film 205 is contaminated with the amine component. In the patterning step of the second resist film 205 to be performed thereafter, the exposure generates an acid catalyst in the resist film, and the action of the acid catalyst accelerates the solubility of the exposed portion to a developing solution, so that the exposed portion is selectively etched by development. Accordingly, if the second resist film 205 is contaminated with the amine component as described above, the acid catalyst in the second resist film 205 reacts with the amine component to lose its function as the acid catalyst. For this reason, the second resist film 205 has not sufficiently patterned, thus causing a portion of the second resist film 205 to remain as shown in FIG. 14 which should be removed normally. In this case, the subsequent etching treatment using the second resist film 205 as a mask has not been properly performed, failing to form the wiring groove 206 in a proper shape.